Nearly 100% selective and visible-light-driven methane conversion to formaldehyde via. single-atom Cu and W(δ+)

Direct solar-driven methane (CH(4)) reforming is highly desirable but challenging, particularly to achieve a value-added product with high selectivity. Here, we identify a synergistic ensemble effect of atomically dispersed copper (Cu) species and partially reduced tungsten (W(δ+)), stabilised over an oxygen-vacancy-rich WO(3), which enables exceptional photocatalytic CH(4) conversion to formaldehyde (HCHO) under visible light, leading to nearly 100% selectivity, a very high yield of 4979.0 μmol·g(−1) within 2 h, and the normalised mass activity of 8.5 × 10(6) μmol·g(-1)(Cu)·h(−1) of HCHO at ambient temperature. In-situ EPR and XPS analyses indicate that the Cu species serve as the electron acceptor, promoting the photo-induced electron transfer from the conduction band to O(2), generating reactive •OOH radicals. In parallel, the adjacent W(δ+) species act as the hole acceptor and the preferred adsorption and activation site of H(2)O to produce hydroxyl radicals (•OH), and thus activate CH(4) to methyl radicals (•CH(3)). The synergy of the adjacent dual active sites boosts the overall efficiency and selectivity of the conversion process.